The Integrated Public Use Microdata Series (IPUMS) consists of fifty-nine high-precision samples of the American population drawn from fifteen federal censuses, from the American Community Surveys of 2000-2007, and from the Puerto Rican Community Surveys of 2005-2007. Some of these samples have existed for years, and others were created specifically for this database. These samples collectively constitute our richest source of quantitative information on long-term changes in the American population. However, because different investigators created these samples at different times, they employed a wide variety of record layouts, coding schemes, and documentation. This has complicated efforts to use them to study change over time. The IPUMS assigns uniform codes across all the samples and brings relevant documentation into a coherent form to facilitate analysis of social and economic change.

BUENOS AIRES — Their disappearance is one of Argentina’s most enduring mysteries. In 1810, black residents accounted for about 30 percent of the population of Buenos Aires. By 1887, however, their numbers had plummeted to 1.8 percent.

So where did they go? The answer, it turns out, is nowhere.

Popular myth has offered two historical hypotheses: a yellow fever epidemic in 1871 that devastated black urban neighborhoods, and a brutal war with Paraguay in the 1860s that put many black Argentines on the front lines.

But two new studies are challenging those old notions, using distinct methods: a door-to-door census to determine how many Argentines consider themselves black, and an analysis of DNA samples to detect traces of African ancestry in those who consider themselves white.

The results are only partially compiled, but they suggest that many of the black Argentines did not vanish; they just faded into the mixed-race populace and became lost to demography. According to some researchers, as many as 10 percent of Buenos Aires residents are partly descended from black Argentines but have no idea.

“People for years have accepted the idea that there are no black people in Argentina,” said Miriam Gomes, a professor of literature at the University of Buenos Aires who is part black and considers herself Afro-Argentine. “Even the schoolbooks here accepted this as a fact. But where did that leave me?”…

…”Argentina was interested in presenting itself as a white country,” said George Reid Andrews, a history professor at the University of Pittsburgh who has specialized in black history in Latin America. “Its ideologues and writers put a great emphasis on the yellow fever epidemic and the war, and it was feasible to pretend that the black population had simply disappeared as immigration exploded.” …

… But personal definitions do not count when analyzing DNA, which is what a group of scientists from the University of Buenos Aires and Oxford University in England did earlier this year. After collecting blood samples at a local hospital, they searched for genetic markers that indicate African ancestry. The results, to be published this year in the American Journal of Physical Anthropology, suggested that 10 percent of those who identified themselves as white were, in part, descendants of black Argentines.

“A lot of people were very surprised by this,” said Francisco R. Carnese, a geneticist at the University of Buenos Aires and co-author of the study. “When you walk around Buenos Aires, you don’t see signs of African ancestry. But you see it in the genes.” ..